Onboard Maven restores to CFS

[ahmedmuhsin]

Summary

• Route Maven dependency and plugin restores through the upstream-public CFS feed.
• Override the snapshot plugin repository inherited from java-8-parent.
• Install the repository Maven mirror and authenticate it before public and official CI builds.
• Resolve the Application Insights agent through Maven instead of downloading it directly from Maven Central.
• Add local credential-provider helpers for ingesting uncached packages.

This follows the Maven onboarding pattern from Azure/azure-functions-openai-extension#218.

Validation

• Authenticated CFS mvn clean package -DskipTests -Dgpg.skip=true -Dspotbugs.skip=true
• Application Insights agent copy through Maven and CFS
• Verified the effective dependency, plugin, and mirror configuration
• Exercised the PowerShell credential-provider bootstrap using a disposable Maven repository
• Validated PowerShell and Bash helper syntax